A referendum on the terms of departure from the EU could be a good idea.

No, no it wouldn't. Are you aware of the rules of negotiation? DO NOT SEND SOMEONE TO NEGOTIATE UNLESS THEY HAVE THE POWER TO SIGN THE AGREEMENT, such a referendum would make the British people the signer, not May, even though I am a direct democrat myself, that is a terrible idea because it gives the EU much more negotiating power for no gain.

A referendum on the terms of departure from the EU could be a good idea.

However what would happen if we voted against it, surely it would lengthen the process of withdrawing and create further economic uncertainty.

We can probably trust the current Conservative government to negotiate a pretty good deal but there's no reason to object to this sort of safeguard.

Above all, the departure must be genuine and 'take back control' to a noticeable extent, any watered down arrangement deserves immediate rejection.

No point in a referendum on the final outcome of the deal really. For one it would frustrate the EU beyond belief seeing the deal terfed out by the British public immediately, with two years of diplomatic capital flushed down the drain in that moment. And secondly, this won't be the last bit of diplomacy we ever conduct with the EU. Subsequent governments will continue to revise the relationship drawn up between the May administration and the EU for decades to come.

I'd rather have a 'soft Brexit' deal pass and amend it later than throw any deal out into the wind. Having some kind of formal relationship established post-Brexit creates a good rock to work off of.